# Quantum mechanics: the theoretical minimum what you need to know to start doing physics

Sep 24, 2022

In quantum mechanics, particles (like atoms and photons)ooze and change their states as they come into and leave contact with other particles. The behavior of a particularly stable subatomic particle, like an electron in an atom, can be predicted by its quantum state—a combination of its position, momentum, and energy.

But what if you want to know what will happen to a group of particles, or to a single particle that is moving around and interacting with other particles? In that case, you need to use the laws of quantum mechanics.

The first law of quantum mechanics is the Heisenberg uncertainty principle, which says that you can never know both the position and momentum of a particle with absolute certainty. The second law is the Schrödinger equation, which describes how a particle’s wave function changes over time.

The wave function is a mathematical description of a particle that includes all of the information that can be known about the particle. It is a complex number, which means that it has a real and imaginary component. The real component describes the position of the particle, and the imaginary component describes the momentum.

The square of the wave function (the absolute value) gives the probability of finding the particle in a particular place. So, if the wave function of an electron is spread out over a large area, it means that the electron is likely to be found anywhere in that area. If the wave function is concentrated in a small area, it means that the electron is more likely to be found in that small area.

The wave function of a particle can be changed by interacting with other particles. For example, when an electron collides with a photon, the photon transfers some of its energy to the electron, and the electron’s wave function changes.

The wave function can also be changed by measurement. When you measure the position of a particle, you change its wave function. The act of measurement creates a relationship between the observer and the observed—the quantum state of the particle is affected by the act of observation.

Quantum mechanics is the branch of physics that studies the behavior of matter and energy in the presence of an observer. It is the foundation of modern physics and the theory of the wave-particle duality.

## Other related questions:

### Q: How do I start theoretical physics?

A: There is no one “right” way to start learning theoretical physics, as it is a vast and complex subject. However, some ways to begin learning about theoretical physics include studying the fundamental principles of physics, such as Newton’s laws of motion and Einstein’s theory of relativity; taking advanced physics courses; and reading popular books and articles on theoretical physics. Additionally, attending lectures and conferences on theoretical physics can be a great way to learn from experts in the field.

### Q: How many theoretical minimum books are there?

A: There is no definitive answer to this question as the number of theoretical minimum books depends on the particular field of study. However, it is generally agreed that there are at least four theoretical minimum books in mathematics, physics, and computer science.

### Q: Can you learn quantum mechanics without classical mechanics?

A: No, you cannot learn quantum mechanics without first learning classical mechanics.